The present invention relates to a portable electronic device which is capable of controlling input operation required to view images and listen to music, a method of controlling input operation on such a portable electronic device, and a program for controlling input operation on such a portable electronic device.
Heretofore, laptop PCs (Personal Computers) employ a touch pad for moving a cursor, a scroll bar, or the like in images displayed on the display monitor. The touch pad detects the position in which a user's finger or the like touches the touch pad and displays a cursor in an image displayed on the display monitor depending on the touched position. Specifically, when the user's finger touches the touch pad, the electrostatic capacitance between electrodes in the touch pad changes and the touch pad detects the change in the electrostatic capacitance, thereby detecting the position of the user's finger on the touch pad.
There is known an input device including a combination of such a touch pad and a set of operation buttons such as a keyboard. Specifically, sensors for detecting electrostatic capacitance changes are disposed beneath or within keyboard keys. For details, see Japanese Patent Laid-Open No. 2003-223265 (FIGS. 1 and 10). Particularly, the publication discloses an application wherein the input device is reduced in size and incorporated in a cellular phone set.
If the input device is reduced in size and incorporated in a cellular phone set, however, the area of contact with the user's finger on the input device is greater than the area of each of the operation buttons, and the operation buttons are spaced at reduced intervals. Accordingly, the user finds it difficult to touch a desired one of the operation buttons precisely.
An input device, such as a touch pad, for detecting an electrostatic capacitance change is designed to detect the coordinates of the center of gravity of an area where the user has touched the input device because the electrostatic capacitance change is greatest in that area. Since the user's finger is more sensitive toward its fingertip, a spot on the input device that the user is thinking as touching and the area of the input device that is actually touched by a finger portion including the fingertip and the finger cushion may possibly be different from each other. When such a discrepancy occurs, the coordinates of the center of gravity of the area that is actually detected and the coordinates of the spot that the user intends to touch deviate from each other, possibly resulting in the detection of an undesirable operation button as being touched. If the input device is a device for changing the position of an object such as a cursor, a pointer, or the like displayed depending on the coordinates that are detected, then such an object may be displayed in a position not intended by the user when an undesirable operation button is detected as being touched.
On the other hand, if the input device is a device for reflecting a movement of the user's finger in a displayed image, then the input device may display a moved distance different from the moved distance intended by the user or may even display a movement not intended by the user due to fluctuations of detected values such as of electrostatic capacitance and noise.